Preparation of aluminum having block texture

ABSTRACT

A process for the production of thin aluminum strips or sheets having a thickness less than 0.2 mm comprising the steps of hot rolling, cold rolling and recrystallization annealing wherein the aluminum strips or sheets are subjected to cold rolling, annealing and cold working between hot rolling and final recrystallization annealing.

United States Patent 1191 Boutin 14 1 Feb. 13, 1973 PREPARATION OF ALUMINUM [56] References Cited HAVING BLOCK TEXTURE UNITED sTATEs PATENTS [76] Invent Franmis Regis fl' we de la 2,161,419 6/1939 Kipper-man etal. ....14s 11.5 A Gare 3S'VmeU'SUY'BWYbYC 3,266,945 8/1966 Helling eta]. ....l48/1 1.5 A France 3,351,442 11/1967 Hooper ..l48/l 1.5 A

[22] Filed: Aug. 20, 1971 Primary ExammerW. W. Stallard pp No.1 173,698 AttorneyMcD0ugall, Hersh & Scott [30] Foreign Application Priority Data [57] ABSTRACT Nov. 16 1970 France ..7040921 A PmcesS the Producfim of thin aluminum rips or sheets having a thickness less than 0.2 mm compris- 52 us. (:1. ..14s/11.5 A ing h Steps of hot mlling and recrystal- [51] 1m. Cl. ..C22f1/04 annealing wherein the aluminum strips 58 Field of Search ..148/ll.5 A sheets subiwed 011mg, annealing and cold working between hot rolling and final recrystallization annealing.

5 Claims, No Drawings PREPARATION OF ALUMINUM HAVING BLOCK TEXTURE This invention relates to a process for the production of thin aluminum strips or sheets with a predominant proportion of so-called block crystalline texture.

The block texture, also known as the cubic texture, of a metal such as aluminum denotes the case where the crystals are oriented in such a way that their crystallographic plane of Miller indices (100) is substantially parallel to the plane of the sheets, while their crystallographic direction of Miller indices[l0] is substantially parallel to the direction in which the sheet is rolled. A texture of this kind is represented by the symbol (100) [010].

The crystalline texture of aluminum in its annealed state is generally complex. It can comprise the block texture and other types of texture such as those where the plane (123) or the plane (112) is parallel to the plane of the sheet.

Various studies have been made on the subject of the proportion of block texture in strips or sheets of aluminum. These studies were directed either to the disappearance of the stamping points and, in this case, attempts were made to obtain a percentage of block texture which compensated the other textures and which, as a result, did not exceed 50 percent of block texture, or to producing sheets intended to be used for the production of electrolytic condenses after having been subjected to a chemical or electrochemical attack known as etching, followed by the formation of a layer of alumina. In this particular case, certain authors have recognized that it is advantageous to have the block texture proportion as high as possible so as to obtain the largest effective surface after etching.

It is apparent from these studies (cf. Z. Metallkunde,Vol. 55( 1964) No. 6, pp.347-350) that the maximum block texture percentage which it is possible to obtain by cold working and recrystallization annealing is governed by the final thickness of the strip or sheet; the thinner the sheet, the more difficult it is to see the block texture.

Attempts have been made to increase the proportion of block structure by intermediate annealing treatments during cold-rolling.

in Z. Metallkunde, Vol. 59(1968), No. 3, pp. 236240,reference is made to intermediate annealing treatments carried out 'for several hours at temperatures equal to or higher than 300 C. It is possible in this way to obtain high proportions of block texture in relatively thick strips or sheets: at least 0.5 mm in the case of refined aluminum, several millimeters where aluminum with a 0.5 percent impurity content is used, although with lesser thicknesses the percentage obtained decreases rapidly.

According to these studies, therefore, it is impossible to obtain even with refined aluminum, any more than 50 to 55 percent of block texture for thicknesses of the order of 0. 1 mm.

It is accordingly an object of the present invention to provide a method for the treatment of aluminum strips or sheets which overcomes the foregoing disadvantage, and it is a related object of the invention to provide a method for the production of aluminum strips or sheets having a thickness of less than 0.2 mm which have a significantly increased block texture component, such as a block texture component in excess of percent for ultimate thickness of 0.1 mm and exceeding 60 percent for ultimate thickness of 0.05 mm.

The process according to the invention is distinguished by the fact that, between hot-rolling and the final recrystallization annealing treatment, the metal is subjected l. to cold rolling with a cold-working rate, defined as the ratio between the variation in thickness and the final thickness, of greater than 1,000 percent and preferably greater than 2,000 percent.

2. an annealing treatment at a temperature of from 180 to 350 C. for a period between a minimum varying from 5 seconds at 350 C. to 5 hours at 180 C., preferably being carried out for a period of from 1 to 25 hours at a temperature of from 200 to 270 C., and

3. cold-working to anextent of from 5 to 35 percen and preferably from 5 to 20 percent which can be obtained by cold-rolling or drawing.

The initial stages of cold rolling can be interrupted by an annealing treatment carried out over a period greater than or equal to 1 hour at a temperature of from 300 to 350 C.while maintaining a subsequent cold-working rate of greater than 1,000 percent without any adverse affect upon the final result.

The same effect is obtained where the final annealing treatment is immediately preceded by a degreasing operation in which a temperature of from to 200 C. is maintained.

Having described the basic concepts of the invention, reference is now made to the following examples, which are provided by way of illustration and not by way of limitation, of the practice of the invention.

EXAMPLE 1 The influence which the conditions under which intermediate annealing and final rolling are carried out have upon the proportion of block texture was studies in a first series of tests, the other treatment parameters, especially the cold-working rate before intermediate annealing being kept constant.

Ablank of aluminum with a total, iron, silicon and copper content of 0.007 percent hot-rolled to a thickness of 3.5 mm was used for the tests.

This blank was cold-rolled to a thickness of 0.115 mm. corresponding to a cold-working rate of 2,950 percent. Intermediate annealing was carried out under the variable conditions indicated in Table 1 below in a static furnace in coil form. After this annealing treatment, followed by cooling in air, various cold-rolling operations were carried out in the main rolling direction in order to determine the cold-working rate which corresponds to the maximum block texture percentage after final annealing.

The final recrystallization annealing treatment was carried out in a nitrogen-filed static furnace in coil form for a period of 2 hours at 450 C. Cooling after annealing was carried out in the open air.

The crystalling texture obtained is monitored by a known micrographic method in which so-called corrosion figures characteristic of the crystalline orientation of the grains are made to appear on the surface of a sample of thin sheet by treatment in an aggressive chemical reagent, and the proportion by volume of crystals oriented in the direction (l)[010] determined.

Table I below gives the results obtained in dependence upon the intermediate annealing conditions by comparison with a sheet treated in the absence of intermediate annealing.

TABLE I Optimum coldworking rate lnter- (after intermediate mediate an- Block texture Modification Anneal nealing) component after produced by ing final annealing the process No annealing 50% 16 hrs. slight improveat 150C. 30% 55% ment( 16 hrs. marked improveat 200C. to 25% 90 to 95% ment(+ 40-45%) 1 hr. marked improveat 250 C. 5 to 25% 90% ment(+ 40%) 1 hr. marked improveat 270C. 10 to 20% 85 to 90% ment(+ 35 -40%) 1 hr. slight improveat 300C. 65% ment(+ 15%) l hr. slight deteriorat 350C. 15% 45% ation( 5%) 4 min. distinct improveat 350C. 15% 75% ment(+ 25%) sec. marked improveat 350C. 15% 85 to 90% ment(+ 35-40%) It should be noted that brief annealing treatments carried out at temperatures of from 300 to 350 C. require rapid increase in temperature which can produce an abnormal growth of less desirable recrystallized grains.

EXAMPLE 2 In order to demonstrate the influence upon the coldworking rate after intermediate annealing for a constant final thickness, the intermediate annealing and final annealing conditions being constant, a blank hotrolled to a thickness of 3.5 mm, identical with that of the preceding example, was taken and subjected to the cold-rolling treatments indicated in Table II, the intermediate annealing treatment being carried out over a period of 24 hours at 200 C. while the final annealing treatment was the same as in the preceding example. It can be seen that, when the original thickness and the final thickness are the same (as mentioned earlier on,it is known that the block texture component is governed by the final thickness), the cold-working rate before intermediate annealing decreases when the cold-working rate after intermediate annealing increases.

The effect of the treatment according to the invention on products of variable thickness was investigated in a further series of tests.

TABLE III Cold- Cold- Working Block Thickworking rate texture ness rate after component Initial after during inter- Final after thick initial initial mediate thickfinal ness rolling rolling annealing ness annealing 3.5 mm 0.230 mm 1460% 15% 0.200 mm 95-10096 3.5 0.185 1790% 15% 0.160 95-100% 3.5 0.115 2950% 15% 0.100 90-95% 3.5 0.057 6040% 15% 0.050 60-65% Blanks hot-rolled to a thickness of 3.5 mm identical with those of the preceding examples were again used. These blanks were cold-rolled to a varible thickness greater by 15 percent than the final thickness indicated in Table 111 above. After intermediate annealing for 24 hours at 200 C., the blanks were rerolled with a coldworking rate of 15 percent and, finally, were subjected to final recrystallization annealing for 1 hour at 450 C EXAMPLE 4 The effect of the treatment according to the invention upon aluminum of different purity was investigated in another test.

A blank of aluminum with a total iron, silicon and copper content of 0.04 percent hot-rolled to a thickness of 3.5 mm was used for the test; It was coldrolled to a thickness of 0.14 mm, after which it was subjected to intermediate annealing for 16 hours at 250 C. and then to rolling to a thickness of 0.12 mm. The final annealing treatment was carried out in a nitrogen atmosphere over a period of 2 hours at 450 C. The block texture component obtained amounted to percent which is remarkable in view of the low purity of the metal.

It will be apparent that various changes and modifications can be made in the details of procedure and use without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. In a process for the production of thin aluminum strips having a thickness less than 0.2 mm containing a predominant texture wherein a thin aluminum strip or sheet is subjected to hot-rolling, cold-rolling including an intermediate annealing treatment and then recrystallization annealing at a temperature within the range of 300 to 650 C., the improvement comprising subjecting the strip of sheet, between hot-rolling and recrystallization annealing, to the successive steps of cold-rolling with a cold-working rate of greater than 1 ,000 percent,

annealing at a temperature of from 180 to 350 C. for a period between a minimum varying from 5 seconds at 350 C. to 5 hours at 180 C and a maximum varying from 3 minutes at 350 C. to 150 hours at 180 C., and

cold-working to an extent of from 5 to 35 percent.

2. A process as defined in claim 1 wherein the coldworking rate before intermediate annealing is greater 1 than 2,000 percent.

0 defined in claim 1.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 716,419 Dated February 13, 1973 Inventor(s) Francois Regis BOUTIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 16, after "l80C.," please insert and a maximum varying from 3 minutes .at 350C. to

150 hours at 180C Column 2, line 42, change "studies" to studied Signed and sealed this 27th day of November 1973 (SEAL Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents 

1. In a process for the production of thin aluminum strips having a thickness less than 0.2 mm containing a predominant texture wherein a thin aluminum strip or sheet is subjected to hot-rolling, cold-rolling including an intermediate annealing treatment and then recrystallization annealing at a temperature within the range of 300* to 650* C., the improvement comprising subjecting the strip of sheet, between hot-rolling and recrystallization annealing, to the successive steps of cold-rolling with a cold-working rate of greater than 1,000 percent, annealing at a temperature of from 180* to 350* C. for a period between a minimum varying from 5 seconds at 350* C. to 5 hours at 180* C., and a maximum varying from 3 minutes at 350 C. to 150 hours at 180* C., and cold-working to an extent of from 5 to 35 percent.
 2. A process as defined in claim 1 wherein the cold-working rate before intermediate annealing is greater than 2,000 percent.
 3. A process as defined in claim 1 wherein the intermediate annealing treatment is carried out over a period of 1 to 25 hours at a temperature of from 200* to 270* C.
 4. A process as defined in claim 1 wherein the cold-working rate after intermediate annealing is between 5 and 20 percent. 